This invention relates to liquid dispensers and, more particularly, liquid dispensers to dispensing liquid as a foam.
Liquid dispensers for dispensing soaps and other similar fluids in liquid form are known. For various reasons in some applications, it is preferable to dispense soaps and other similar fluids in the form of a foam. Generally, in the form of a foam, less soap liquid is required to be used as contrasted with the soap in the liquid form. As well, soap as foam is less likely to run off a user""s hands or other surfaces to be cleaned.
Known liquid dispensers for dispensing foams include the dispenser taught by U.S. Pat. No. 5,445,288 to Banks, issued Jul. 29, 1995. A disadvantage which the present inventor has appreciated with dispensers such as those taught by Banks is that when used with a non-collapsible or rigid sealed container of soap liquid, a vacuum comes to be developed in the container which renders the dispenser inoperative.
Known liquid dispensers for dispensing liquids without foaming of the liquids are also known. The present inventor has also appreciated that many such dispensers also suffer the disadvantage that they are not suitable for use with non-collapsible or rigid sealed containers since the pumps develop a vacuum in the container. Non-collapsible or rigid sealed containers have the disadvantage of requiring various one-way valve mechanisms to permit air to enter the containers under vacuum to equalize the pressure in the containers with atmospheric pressure. Such one-way valves typically suffer the disadvantage that they maintain at least some vacuum pressure differential in the container and with many viscous soaps, the presence of even a slight vacuum can negatively affect dispensing.
The present inventor has also appreciated that known soap dispensers suffer the disadvantage that they do not permit for positive replacement of air for liquid dispensed from a liquid reservoir and/or do not permit a positive pressure to develop in a container.
To at least partially overcome these disadvantages of previously known devices, the present invention provides a pump for dispensing fluid which provides for a positive replacement of liquid dispensed from a container, preferably with atmospheric air. The present invention also provides a pump for dispensing liquid in the form of a foam preferably without creating a vacuum in a non-collapsible or rigid sealed container.
An object of the present invention is to provide an improved pump for dispensing a liquid.
Another object is to provide an improved pump for dispensing a liquid in the form of a foam.
Another object is to provide a pump for dispensing liquid from a non-collapsible or rigid sealed container without creating a vacuum in the container.
Another object is to provide a pump which provides for positive replacement of liquid dispensed from a container by atmospheric air.
Accordingly, in one aspect, the present invention provides a pump for dispensing liquid from a reservoir comprising:
a piston chamber-forming member having an inner cylindrical chamber and an outer cylindrical chamber each having a diameter, a chamber wall, an inner end and an outer end;
the diameter of the inner chamber being less than the diameter of the outer chamber,
the inner chamber and outer chamber being coaxial with the outer end of the inner chamber opening into the outer chamber;
an inner end of the inner chamber in fluid communication with the reservoir;
a piston-forming element received in the piston chamber-forming member axially slidable inwardly and outwardly therein between an outward extended position and an inward retracted position;
the piston-forming element having an axially extending hollow stem having a central passageway closed at an inner end and having an outlet proximate an outer end;
an inner disk on the stem extending radially outwardly from the stem adapted to engage to the chamber wall of the inner chamber;
an intermediate disk on the stem extending radially outwardly from the stem adapted to engage the chamber wall of the inner chamber, the intermediate disk spaced axially outwardly from the inner disk relative the inner end of the stem;
an outer disk on the stem spaced axially outwardly from the intermediate disk and extending radially outwardly from the stem into engagement with the chamber wall of the outer chamber to prevent fluid flow outwardly therebetween;
an inlet located on the stem between the outer disk and the intermediate disk in communication with the passageway;
in the retracted position, the intermediate disk is received in the inner chamber to prevent fluid flow from the outer end of the inner chamber outwardly therepast and the inner disk does not prevent fluid flow between the reservoir and the inner chamber therepast via the inner end of the inner chamber;
in the extended position, the inner disk is received in the inner chamber to prevent fluid flow from the inner end of the inner chamber inwardly therepast and the intermediate disk does not prevent fluid flow between the inner chamber and the outer chamber via the outer end of the inner chamber.
Preferably, the pump includes a porous member in the passageway between the inlet and the outlet for generating turbulence in fluid passing therethrough to generate foam when air and liquid pass therethrough simultaneously.
In preferred embodiments, the pump assembly provides for direct replacement of volumes of liquid from a reservoir with equal volumes of air preferably at substantially atmospheric pressure, the same pressure or with pressure equalization to be at least equal to atmospheric pressure. A slide arrangement preferably positively displaces liquid from the reservoir and air into the reservoir. The pump draws air from the atmosphere into a chamber from which the air either is available for passage to replace liquid from the reservoir or is pressurized to assist dispensing liquid, preferably, admixing with the liquid to provide foaming. Gravity separation of air and liquid to be dispensed is used to replace liquid with air in the reservoir and to selectively place air and liquid into communication with passageways for ejection.